Process for the manufacture of films, foils, bands, and the like from cellulose solutions



y 1943- v E. C-ZAPEKI- 2,318,552

PROCESS FOR THE MANUFACTURE OF FILMS, FOILS; BANDS,

AND THE LIKE FROM CELLULOSE SOLUTIONS Filed Dec. 17, 1956 Inventor:

Patented May' l, I943 uiNirEo STATES PATEN T OFFICE PROCESS FOR THEMANUFACTURE OF FILMS, FOILS, BANDS, AND THE LIKE FROM CELLULOSESOLUTIONS Emil Czapek, New York, N. Y.

Application December 17, 1936, Serial No. 116,290 In Germany December17, 1935 4 Claims. This invention relates to a process for themanufacture of films, membranes, bands, sheets and the like fromsolutions of cum-ammonium cellulose.

The principle underlying the manufacture of film-like bands fromcellulose solutions by known processes, such as aredescribed in GermanPatent,

, Nos. 237,152,249356, 421,383 and elsewhere, is

that the coagulation of the solution, the shaping of the film and theconsolidation thereof, are carried out in the same working stage. Whenworking in accordance with the first two of the afore-- said processes,the conversion of the cellulose solution into the film is carriedout-while freely suspended in' the coagulation bath or only lightlysupported by guide rollers, which merely serve to protect delicatemembranes from breaking. When the last of the aforesaid processes is em-O, .ployed, the film is left on the moulding drum from the time of itsformation until the complete penetration of the precipitation liquid.

The progress of the reactions occurring in ternally in any way except byalterations in the chemical reagents or alteration -of theirconcentratio'n.-

The present invention on the other hand,- opens up the possibility ofinfluencing the film during-its formation. This is ell'ected inaccordance with the invention by dealing separately .with the'processesoccurring during its formation, by means of a method which difiersfundaprocess and of the embodiments of the machine for carrying out theprocess illustrated in the accompanying drawing, in which Figure 1 is adiagrammatic elevation of apparatus made according to one embodiment forcarrying out the process; and

Fig. 2 is a similar diagrammatic elevation of an apparatus madeaccording to another em bodiment.

According to the invention, the cuprammonium cellulose solution isapplied in known these processes can scarcely be controlled ex mentallyfrom the previously known processes.

Among the objects of the present invention it is aimed to provide animproved process which will permit dividing one of the main reactionsthereof into 'a succession of steps instead of combining them in onesole step, with a view to increasing the output of machines for carryingout this process and thereby-to speed up or expedite the operation ofsuch machines for carrying out such processes. I It is still anotherobject of the present. in vention to provide an improved process wherebycert in of the reactions may be divided into successive steps toincreasethe flexibility of the process to facilitate regulating-the sameaccording to the thickness of film to be produced with a certainpredetermined uniformity and consistency and according to theingredients used.

, These. and other features, capabilities and advantages of the machinesfor carrying out the -process constituting the invention will appearfrom the sub-joined detail description of the This film, which is stillsoft and plasticinternally and can be made to redissolve, for example bymoistening-with water, is thenpassed on further supports, such as.conveyor belts or rollers, through a supplementary coagulation bath, inwhich it can then be subjected toa .second precipitating action varyingfrom the preliminary coagulation.

Theptreatment with dilute acids for the purpose of the furtherconsolidation of the film and removal of the copper therefrom, whichotherwise takes place inknown processes immediately after thecoagulation, 'follows only after this treatment.

The purpose of this separate and regulable treatment is manifold. In.the manufacture of cellulose films and the. like from cuprammoniumcellulose solutions the removal of the ammonia atthe correct timeiand toan extensive degree from the coagulated structure plays an importantrole. If for example the ammonia be entirely removed immediately afterpouring out on tov the support, i. e.,before the. f

coagulation, the film is extremely difficult to detach from the support.The same thing occurs if the coagulation be effected with bathconcentrations of dilute liquor, when the required removal of ammoniafrom, the film occurs too rapidly. 1 In both cases the coagulatedproductbecomes brittle in addition, so that whe'n'li'fte'd off from the supportit breaks and splinters like glass.

If on the other hand the ammonia be removed I the ing approximately 6%to an inadequate extent from the solution, the

the film can be detached from the support. The

subsequent second coagulation proper is then adjusted to the ammoniaconcentration still present in the film in such a way that the ammoniacan escape or is removed from the coagulated structure to the desireddegree. For this purpose, for the second" coagulation a liquor ispreferably selected of lower concentration than for the preliminarycoagulation, in order to facilitate the diffusion of the ammonia out ofthe film. With this treatment it is now also possible to interpose shortor long intermediate stretches of the web where .the ammonia can escapeinto the air. The use of the word "coagulation" is here to be definitelydistinguished from the word. regen-' eration" which latter is used tocharacterize only the treatment in which the previously coagulated filmis being transformed into a cellulose hydrate.

The process of the present invention first of all enables cuprammoniumsolutions to be employed having a higher ammonia content than usual,also permits a better and more thorough removal of the ammonia from thecoagulated solutions, and finally enables the output of the machinestobe considerably increased and the speed of working to be raised,because only a preliminary coagulation now takes place on the samesupport, on which otherwise the complete coagulation must be carried outin'know'n manner. This takes much less time. The fact that the film isdetached from the support in a perfect manner and better than in theknown processes is a further advantage which likewise benefits the speedof production.

The invention will now be described with reference to the followingexample:

A solution of cuprammonium cellulose, containof cellulose and 7% ofammonia, is spread out by means of a slot nozzle or other suitablespreading device a on the cylindrical shell surface of a moulding drum(Fig. 1) or of a moulding belt b .(Fig. 2). Through the rotation of thehorizontally mounted drum b, the solution arrives shortly after thespreading in a. coagulation bath 0 consisting of a soda lye of 6%strength, through which it is passed within a few seconds. After leavingthis bath the film, now superficially coagulated, is detached from thepouring support and passed on to a take-up dr'um' d or the-like, fromwhere it is passed along on suitable rollers e or suitable supports.

During this movement the film is'first led freely through the air toenable it to give of! a part of the ammonia present in the interior andis then dipped into a bath f of a soda lye of 3% in which it remainsuntil the precipitation is completed. It then passes into a bath phuricacid of 2% strength for the purpose of regeneration and removal of thecopper. The premature removal of the film from the support also permitsthe stretching of the film after such removal-similarly to the stretchspinning process for rayon-for the purpose of increasing its strength,by giving the take-up drum d an advance. Fig. 1 shows the method ofworking when strength,

g of sula moulding drum is used, and Fig, 2 shows the use of a mouldingbelt and a special-device for obtaining an open air run after thedetachment dr and d2.

Subsequent to the regenerating and de-copperizing step which maytakeplace in the bath g aforesaid, as is customary, the resulting layer willbe subjected to further treatment including washing, softening anddrying.

I claim:

l. A process for the manufacture of films, foils.

membranes, bands and the like from solutions of cuprammonium cellulose,which comprises pouring a cellulose solution onto a support, ad-

vancing the solution so supported through a preliminary coagulating bathcontaining an aqueous alkaline solution, subjecting the solutionsoadvanced to a preliminary coagulation while-being advanced through suchpreliminary bath to produce a self-sustaining layer readily detachablefrom the support, detaching the layer' so produced fromthe support,effecting a final coagulation of the layer so producedin a second bathcontaining a coagulating fiuid of a similar nature to that in the firstbath but of a lower concentration than that in the first bath, and thereupon subjecting the layer so produced to further successive treatmentsincluding regenerating and de-copperizing, washing and drying.

2. A process for the manufacture of films, foils, membranes, bands andthe like'from solutions oi cuprammonium cellulose, which comprisespouring a cellulose solution onto a support, advancing the solution sosupported through a preliminary coagulating bath containing an aqueousalkalinesolution and subjecting the solution so advanced to apreliminary coagulation while being advanced through such bath toproduce a self-sustaining layer readily detachable from the support,detaching the layer so produced from the support, removing the bulk ofthe ammonia from the layer so produced and thereby effecting finalcoagulation of the layer so produced in a second bath containing acoagulating fluid of a similar nature to that in the first bath but of alower concentration than that in the first bath. and thereuponsubjecting the layer so produced to further successive treatmentsincluding regenerating and de-copperizing, washing and drying.

3. A process for the manufacture of films, foils, membranes, bands andthe like from solutions of cuprammonium cellulose, which comprisespourso produced from the support,effecting final coagulation of thelayer so produced in a second bath containing a coagulating fluid ofsimilar nature to that in the first bath but of a lower concentrationthan that in the first bath, and

, thereupon subjecting the layer so coagulated to further successivetreatments including regenerating and de-copperizing, washing anddrying.

4. A process for the manufacture of ,fllms, foils, membranes, bands andthe like from solutions of cuprammonium cellulose, which comprisespouring a cellulose solution onto a support and spreading it thereonwhile said support and said solution are substantially free ofcoagulating 2,318,852 liquids, whereby said spread solution] adheres tosaid support, advancing the cellulose solution so supported through apreliminary coagulating bath,-and subjecting the cellulose solution soadvanced to a preliminary coagulation while advancing through such bathto produce a partly support, moving said surface at a faster rate thansaid first supportto stretch the'intervening area of the'thus partlycoagulated layer disposed between the two supports, thereupon efiecttngfinal coagulation of the layer so stretched in a second bath, containinga coagulating fluid of a similar nature to that in the first bath andthereupon subjecting the layer so'coagulated to further succes'sivetreatments including regenerating and decopperizingjwashing and drying.

' EMIL CZAPEK.

